To this day there's not a single Apple laptop that ships with built in 4G modems even though that would make sense from a functional point of view. I suspect the reason is not technical but related to IP and pushback from other players in the ecosystem (e.g. operators). As soon as you add 4G/5G to the mix, there are suddenly a lot of sneaky patents that come into play.
At least you can't tell me that nobody in Apple pondered the question "hmm I wonder which of our Mac Book Air customers would not like to be connected anywhere on this planet". The reason this is not a feature is that it would add a lot of cost related to patents and IP licensing. This deal might fix that partially. Software sims have been similarly difficult for the same reasons and another thing Apple has been pushing on lately.
Apple doing this stuff in house means they can push harder on this front.